Yea, that part of Shuri's portrayal was kinda strange. As far as the comics are concern, she never went in Oxford, but studied elsewhere (assumed to be in Wakanda).
Her having a British accent is even stranger, being that she doesn't venture outside of Wakanda much and was raised in Wakanda. Other non-comic book mediums have Shuri with an African accent, so for this show to go a different direction is a bit confusing.
I liked Shuri's portrayal overall, but the accent thing is a detail that hopefully gets fixed eventually.